[solved?] Laptop fan always on (after update)

Hi guys.

after an update (don't know exactly which one, but approximately in the last 2 months) i have my laptop fun always running at mid speed (not the slowest speed, not the fastest, the mid range).my laptop is an acer 5920g, and the fan used to work great (start spinning faster after CPU reached 50°C and slowing down again below that themperature).